Positional criteria for matching ComPRASS candidates to redMaPPer clusters. Panel a: closest redMaPPer cluster to each ComPRASS candidate. Panel b: all the possible redMaPPer counterparts within 10 arcmin of each ComPRASS candidate. Red, blue, and green symbols represent the closest, second-closest, and third-closest counterpart (if it exists), respectively. The black circles identify the pairs that are finally selected. The blue and red coloured crosses in the d <  5 region correspond to associations that satisfy the positional criteria, but that are finally discarded by the richness cut.